Question

In an interesting study by a tobacco company, they found that the mean age when smokers first start to smoke varies in each generation. However, the standard deviation of that age remains constant of around 1.9 years. A survey of 45 smokers of the current generation was done to test if the mean age for starting to smoke is at least 20. The sample mean was 19.5 with a sample standard deviation of 1.5. Do the data support the claim at the 5% level?

Answer 1

This is the left tailed test .

The null and alternative hypothesis is

H₀ : = 20

H_a : < 20

Test statistic = t

= ( - ) / s / n

= (19.5 - 20) / 1.5 / 45

= -2.236

Test statistic = -2.236

df = 44

P-value = 0.0152

= 0.05

P-value <

Reject the null hypothesis .

Data support the claim at the 5% level .